1. Field of the Invention
This invention relates to a point of sale printer for printing information on both sides of a check, and, more particularly, to such a printer having a loop around which the check is fed to invert it between the processes of printing on the two opposites sides.
2. Description of the Related Art
In continuing attempts to provide more efficient and convenient service to customers, many retailers have begun to use point of sale check printers to reduce the time required for a customer to fill out and sign a check. Such a printer automatically enters the date, the total cost of purchases, and the name of the retail establishment to which payment is being made, in the corresponding spaces of a check provided by the customer. The signature line is left blank, to be filled in by the customer after he is presented with the printed check.
Another form of printing performed on a check by the retailer comprises printing the franking information on the reverse side of the check. This information generally indicates that the check is for deposit only or that it is to be deposited to a particular account. While it is not necessary to perform this printing operation at the point of sale, many retail establishments have a policy of printing this information, with a rubber stamp if necessary, at the point of sale, reducing the likelihood of financial losses from checks that may otherwise be stolen without the franking information.
U.S. Pat. Nos. 5,865,547 and 6,109,521 describe duplex point-of-sale check printers including a first document path extending past a print element disposed on one side of the first document path and a second document path formed as a loop extending from an end of the first document path. A check is fed from the first path to the second path and around the loop within the second path, to be fed back into the first path, having been turned over by traveling along the loop. During this process, the check is fed in one direction around the loop, but in both directions along the first document path.
In the apparatus of U.S. Pat. No. 5,866,547, the check is driven within the first document-path by means of a first pair of feed rolls turning to move the check into the second document path. The check is then fed along the second paper path by means of rolls and belts turning constantly to move the check along in one direction around the loop. Before the check enters the first pair of feed rolls, these rolls are moved apart so that they do not drive the check, even through they continue to turn in directions that would drive the check back toward the second document path. In this way, a single rotational drive is used to drive both the first pair of feed rolls and the various elements of the second document path at constant speeds and directions. However, a problem with this method arises from the fact that if a corner or a part of an edge of the check has become folded back, movement of the check may be stopped when the folded part, having a greater effective thickness, is moved into the space between the first pair of feed rolls, resulting in a jammed condition. Another problem with this method arises from the fact that the check must be driven outward, along the first document path, by the drive mechanism of the second document path. In some applications, the first document is too long for this to work. Therefore, an apparatus is needed in which the directions of rotation of the first pair of feed rolls are controlled separately from the directions of the various drive elements in the second paper path.
In the apparatus of U.S. Pat. No. 6,109,521, the first directions of rotation of the first pair of feed rolls are reversed between the process of driving the check into the second document path and the process of removing the check from the second document path. The directions of the first pair of rolls are reversed by reversing a drive motor. The drive elements within the second paper path are driven from a gear attached to a roller within the first pair of feed rolls, through a gear train in which the number of idler gears is changed by one as the directions of the first pair of rollers are reversed, so that the directions in which the various elements within the second document path remain the same. What is needed is a system providing for the reversal of the first pair of feed rolls without requiring the use of a gear shifting transmission.
Other patents describe alternative methods for printing both sides of a check. For example, U.S. Pat. No. 6,299,365 shows a duplex check printer in which an end of the check is folded within a rotor to be fed back into a document path extending by the print head. U.S. Pat. No. 6,296,495 describes a duplex check printer in which the check is fed into diverging document paths, with a single print head being pivoted into place between the document paths to print on both sides of the check.